1. Field of the Invention
The present invention relates to an apparatus for forming an optical aperture. In particular, the present invention relates to an apparatus for forming an optical aperture utilized in a near field device that radiates and/or detects near field light.
2. Description of the Related Art
In order to observe microregions of the sample surface on the order of nanometers, scanning probe microscopes (SPM) such as scanning tunneling microscopes(STM) and atomic force microscopes (AFM) are used. SPM scans a sharpened probe on the sample surface, observes the interaction between the probe and the sample surface such as tunneling current or atomic force, and is able to obtain images with a resolution that depends on the probe tip shape. However, there are relatively severe restrictions on the sample.
Interest has been focused on scanning near field optical microscopes (SNOM) that observe the interaction between the near field generated on the sample surface and the probe, thus enabling the observation of microregions of the sample surface.
In SNOM, near field is irradiated to the sample surface from the aperture formed at the sharpened tip of an optical fiber. The aperture has a size smaller than the diffraction limit of the light introduced into the optical fiber, for example, about 100 nm in diameter. The separation between the aperture formed at the probe tip and the sample is controlled by SPM technology, and is smaller than the aperture size. The spot size of the near field on the sample is approximately the aperture size. Therefore, by scanning the near field that is irradiated on the sample surface, it is possible to observe the optical properties of microregions of the sample.
Not only for microscopes, but also for high density optical data recording is it applicable by introducing light of relatively high intensity through the optical fiber probe towards the sample. Near field with high energy density is generated at the optical fiber probe aperture, and it modifies either the structures or the properties locally of the sample surface. In order to obtain near field of high intensity, efforts have been made to increase the vertical angle.
In these devices utilizing near field, aperture forming is the most important. As one apparatus for forming an aperture, an apparatus disclosed in Japanese Patent Publication No.21201/1993 is known. In the manner of forming the aperture with this apparatus, a pointed light waveguide on which an opaque film is deposited is used as the object for forming the aperture. The method of forming the aperture is that the pointed light waveguide with an opaque film on the point is plastically deformed by pressing the pointed light waveguide against a hard flat plate with a very small amount of pressing, which is well-controlled by a piezoelectric actuator.
Another apparatus for forming an aperture is disclosed in Japanese Patent Laid-Open No. 265520/1999. In the aperture forming apparatus disclosed in Japanese Patent Laid-Open No. 265520/1999, the object which is to have an aperture is the point of a projection which is formed on a plate by FIB(Focused Ion Beam). The method of forming the aperture is that FIB is irradiated on the side of the opaque film on the projection point removing the opaque film on the point.
However, according to the method of Japanese Patent Publication No. 21201/1993, the aperture can be formed on the light waveguide only one by one. Additionally, a piezoelectric actuator having a moving resolution of a few nano meters is needed to control the amount of pressing and thus an aperture forming apparatus has to be placed in an environment which is little influenced by vibration of other devices or air. Furthermore, it takes much time to adjust a waveguide rod to vertically abut on the flat plate. Moreover, in addition to the piezoelectric actuator having a small moving amount, a mechanical translation platform having a large moving amount is needed. Besides, when the pressing amount is controlled by using the piezoelectric actuator having a small moving resolution, a control unit is required and it takes a few minutes to control and form the aperture. Therefore, for aperture formation, a large-scale apparatus such as a high voltage power supply or a feedback circuit is needed. In addition, a problem has arisen that costs for aperture formation are increased.
Additionally, according to the method of Japanese Patent Laid-Open No. 265520/1999, the fabrication object is the projection on the flat plate. However, since the aperture is formed by using the FIB, the time required to form one aperture is as long as ten minutes. Furthermore, because of using the FIB, a sample needs to be placed in vacuum. Thus, a problem has arisen that fabrication costs for aperture fabrication are increased.
The present invention overcomes the problems of the conventional art. An apparatus for forming an optical aperture comprises an object having a tip of conical or pyramidal shape, a stopper having almost the same height as that of the tip and an opaque film formed on the tip, and loading means for displacing a pressing body having approximately a planar part covering the tip and at least a part of the stopper by a force having a component acting toward the tip to form an aperture on the point of the tip. According to the apparatus for forming an optical aperture in the present invention, the displacement of the planar part of the pressing body is controlled by the stoppers which have almost the same height as that of the tip. Therefore, by simply pushing the planar part with a predetermined force it is easily possible to form an optical aperture. Additionally, it is possible to form an aperture in various environments such as in a vacuum, in a solution, and in the air. Furthermore, it does not require any specially designed controller when it is forming an aperture, resulting in simplification of the aperture forming apparatus. Additionally, it is easy to shorten the duration time of imposing the predetermined force, thus shortening the time for aperture formation and decreasing the cost of aperture formation.
A position controller sets a load target point to a load point of the loader. The load target point is disposed on a surface of the pressing body and over top of the tip. It is possible to control the displacement of the pressing body by a predetermined load toward the load target point. Therefore, optical apertures of uniform and minute size can be easily formed, making it easy to improve the yield of formation of optical apertures.
The apparatus has a plurality of the loaders. The loaders are capable of controlling the load for a plurality of load target points at the same time. The load target points are on a surface of the pressing body and over top of the tips. Since the object for aperture formation comprises plurality of tips and stoppers, it is possible to form an optical aperture on each of the plurality of the tips simultaneously by imposing the predetermined force on all the tips simultaneously. As a result, the fabrication time per an aperture can be shortened considerably, and the cost of aperture formation can be decreased.
A position controller for setting a load target point to a load point of the loader. The load target point being on a surface of the pressing body and over top of the tip. An auto-controller controls the loader and the position controller automatically. An automated control of the loading means and the positioning means results in the decrease in the cost of aperture formation.
Displacement of the pressing body, toward the tip for forming an aperture on a point of the tip, is generated by a weight striking against the pressing body. The apparatus for aperture formation has a simple mechanism in which a weight falls freely, thus lowering the cost of aperture formation.
The displacement of the pressing body, toward the tip for forming an aperture on a point of the tip, is generated by a pressure. The apparatus for aperture formation has a simple mechanism with a pressure means, thus making it possible to form apertures with high precision in a stable manner. Besides, by controlling the pressure generated by the pressure means, the amount of the displacement of the pressing body can be determined arbitrarily, thus making it possible to form apertures of various sizes.
The displacement of the pressing body, toward the tip for forming an aperture on a point of the tip, is generated by a weight striking against the pressing body, and the weight falls freely. A constant impact can be imposed by a free-fall of a weight from a predetermined height. The amount of displacement can be kept constant, thus making it possible to form optical apertures with high precision and low cost.
The displacement of the pressing body, toward the tip for forming an aperture on a point of the tip, is generated by a weight striking against the pressing body. The weight falls freely along the arc from a predetermined angle with respect to a fulcrum axis. The impact caused by the collision between the weight and the object for aperture formation can be kept constant easily, thus making it possible and easy to form optical apertures of uniform and minute size, and improving the production yields of aperture formation. Besides, the amount of displacement of the pressing body can be determined arbitrarily by controlling the position of the fulcrum and the weight, thus making it possible to form apertures of various sizes.
The loader works by a spring force of a pressure spring. By controlling the pressure means with the spring force, it is possible to control the amount of displacement of the pressing body, thus making it possible and easy to form minute optical apertures of uniform size, and improve the production yields of the optical aperture formation. Besides, since the amount of the displacement of the pressing body can be controlled by the spring force, it is easy to form apertures of various sizes.
The loader works by magnets being moved by magnetic repulsive or attractive force. By controlling the pressure means with the magnetic force, it is possible to control the amount of displacement of the pressing body, thus making it possible and easy to form minute optical apertures of uniform size, and improve the production yields of the optical aperture formation. Besides, since the amount of the displacement of the pressing body can be controlled by the spring force, it is easy to form apertures of various sizes.
A work has the object for aperture. A magnifying glass measures amount of the work""s curve. A load controller controls a direction of the loader to make the direction being perpendicular to the tip. Even when multiple tips are formed on a substrate, a constant load is applied for individual tip, thus making it possible to form optical apertures in mass production.
A work has the object for aperture, a magnifying glass measuring for amount of the work""s curve. An auto-controller controls the position of the work to make a direction of the loader being perpendicular to the tip. A simple mechanism can control the load direction for individual tip, thus making it possible to form optical apertures with high precision. Besides, an automation of the production process is easy, thus making mass production possible. Optical apertures can be supplied with low cost.
The apparatus has a plurality of the pressing bodies. Multiple apertures can be formed at once, thus making it possible to form many apertures quickly, and lowering the production cost of apertures.
A cleaner cleans a surface of the pressing body. When one presser forms apertures repeatedly, an accretion attached on the surface of the presser hinders the aperture formation. In this invention, a cleaning mechanism cleans the surface of the presser, thus making it possible to form apertures continuously in a stable manner.
A presser presses the pressing body. The presser has a spherical shape facing the pressing body. A limited area of the presser receives the force, thus making it easy to deform the presser. Even when the stopper is higher than the tip, it is possible to form apertures.
A presser displaces the pressing body. A surface of the presser that faces the pressing body is made of a material. The material is softer than the pressing body. Even when the surface of the pressing body is not flat, a uniform force can be applied onto the pressing body, thus making it possible to form apertures of uniform size in a stable manner. A presser displaces the pressing body. The pressing body has a groove of inverted pyramid shape. The presser has a shape that can gear with the groove on the pressing body. The pressure area for the presser can be easily defined, thus making it possible to form apertures with high dimension precision in a stable manner.
A work has the object for aperture formation. A stage for being loaded with the work; wherein the work is fixed on the stage. There is no problem of a variation in the aperture sizes when the substrate curves, which would be caused by a variation in the force onto the light guiding body depending on the location on the substrate. Besides, the apparatus has a simple mechanism with vacuum equipment that can be installed easily to the stage. The uninstallation of the substrate is also easy.